The present invention relates to a diamine compound, and in particular to a diamine compound having two terminated amino groups and flexible oxypropylene linkage.
Wholly aromatic polyamides and polyimides are well established as high-performance materials with excellent thermal stability and mechanical properties. However, these polymers have a demerit of fabrication problem due to their limited solubility and their high melt or softening temperatures. For example, poly(p-phenyleneterephthalamide) (Kevlar), a well known commercial product and used as a high modulus fiber for a variety of applications, is infusible and only soluble in concentrated sulfuric acid. The infusibility and limited solubility of these aromatic polymers are characteristic properties which restrict synthesis, characterization, processing, and applications thereof, especially to those of high molecular weight. Therefore, a great deal of effort has made for improving their processability.
For instance, the incorporation of flexible linkages, such as arylene ether (--O--) [EP 0565352 A2, JP 05262705], methylene (--CH.sub.2 --) [EP 0483954 A1], sulfone (--SO.sub.2 --) [JP 05295262], isopropylidene [--C(CH.sub.3).sub.2 --)] [U.S. Pat. No. 4,410,684, JP 04183721], and siloxane (--Si--O--) [JP 05214100, JP 04189867] into the polymer backbone to increase the overall chain flexibility are disclosed. The presence of flexible segments can decrease the glass transition temperature and/or the melting temperature and in some cases can even improve the solubility of polyamides and polyimides; thus, processable polymers can be obtained. The polymer structural modifications adopted in the prior art were usually employed by the insertion of flexible segments to the diamine monomer which is to be polycondensated with an aromatic dicarboxylic acid or a tetracarboxylic dianhydride to form the polyamide and polyimide, respectively.